Printing machines are well-known, especially flexographic printing machines which are fitted with a large, central support drum which rotates on a horizontal axis and along which moves a strip of material to be printed and a number of printing clusters are on each side of said support drum. Each printing cluster is designed to print, for example, one colour only for which it comprises a printing cylinder bearing a block with the design to be printed and one or more ink-rollers connected to their respective containers of ink of the corresponding colour positioned to ink the corresponding printing cylinder block. Both the inking rollers and the printing cylinder are positioned to turn on axes parallel to the axis of the support drum with means provided for moving the printing cylinder laterally into contact with the support drum and the inking rollers into contact with the printing cylinder or for separating them.
Each block is mounted on a housing which in turn is mounted on a housing-bearing assembly supported at each extremity by existing supports on opposite sides of the printing machine and operated in turn from one of said extremities. The latest developments in flexographic printing machines incorporate means for maintaining the respective housing-bearing assembly projecting outwards by one of its extremities to allow the withdrawal of the corresponding block-bearing housing by the opposing extremity by sliding it axially along the assembly and the positioning of a new housing by reversing the procedure when a printing cylinder is separated from the support drum. Although technically such housing-changing operations can be undertaken with the printer in operation they are extremely dangerous for the operator due to the proximity of the moving support drum. Furthermore, the block-bearing housings can be both large in size and in weight requiring the assistance of a number of workers or the use of lifting devices such as cranes, pulleys etc. adding to the degree of risk with the machine in operation. As a result, in practice, housing-changing operations are undertaken with the machine at rest which brings with it a significant loss of productivity.
U.S. Pat. No. 6,644,188 describes a procedure for changing housings with the printing machine of the type described above operating. The method foresees the installation of a protective screen between an extremity of the printing cylinder and the support drum so as to provide an area of protection sufficient to allow the operator to take hold of said extremity of the cylinder with relative safety whilst the machine is in operation. However, such screens do not provide total protection and, taking into account that there are flexographic printers with ten or more print clusters and that a protective screen is required for each one, the means for mounting and dismounting such screens is of great complexity in relation to the low level of protection offered. Furthermore, even with the use of said protective screens, the inconveniences associated with the difficulty of handling the housings due to their large size and weight, persist.
On the other hand, document WO 03/095207, of which the present petitioner is owner, describes a housing-extraction device comprising an instrument in the shape of a glass adapted to fit the frontal extremity of the housing into its open end locating part of the extremity of the housing-bearing assembly inside said glass form and a means of injecting compressed air using various alternative methods, adapted so as to create air pressure in the interior of the glass-shaped instrument able to make the housing slide axially along the length of the housing-bearing assembly in order to extract it. A further version is known of where the piston of a pneumatic cylinder attached to the instrument in the form of a glass is what thrusts the assembly to move along the housing. However, these devices are only to initiate the sliding motion of the housing which, in general, is difficult to effect manually due to the resistance created by the close fit of the housing on the assembly and the subsequent extraction of the housing which must be done by hand for which purpose one or more handles are foreseen on the glass-shaped instrument.
There is a need for an automatic housing handling and transportation device which permits housing changing operations to be carried out on a printer with the machine in operation which is totally automatic and without the need for operator intervention and automatic movement and storage of housing operations.